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From: toma@tekgvs.LABS.TEK.COM (Tom Almy)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 32-bit addressing on the 80386 in real mode?!?
Keywords: 80386, 32-bit, Real mode
Message-ID: <6692@tekgvs.LABS.TEK.COM>
Date: 18 Jan 90 16:56:14 GMT
References: <8342@portia.Stanford.EDU> <1990Jan18.055726.20604@wam.umd.edu>
Reply-To: toma@tekgvs.LABS.TEK.COM (Tom Almy)
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 23

In article <1990Jan18.055726.20604@wam.umd.edu> walrus@cscwam.umd.edu (Udo Karl Schuermann) writes:
>In article <8342@portia.Stanford.EDU> dhinds@portia.Stanford.EDU (David Hinds) writes:
>>    I think I might have found a trick for allowing 32-bit addressing
>>in real mode on the 80386.  
[long description of "trick" follows]
>>However, I haven't been able to get it to work. 

>I don't have any literature on the '386 but let me take a shot at this.
[shot misses]
>I'm sure I'm not quite right in some of my reasoning, but this is
>probably close enough, especially since I've got no docs on the '386 :)
>Any gurus to set the record straight(er)?

From the Intel 80386 Programmer's Reference Manual, Chapter 14, 80386
Real-Address Mode, "Unlike the 8086 and 80286, 32-bit effective addresses
can be generated (via the address-size prefix); however, the value of a 32-bit
address may not exceed 65535 without causing an exception."

In other words, "forget it."  80386 protected mode is the *only* way to go.

Tom Almy
toma@tekgvs.labs.tek.com
Standard Disclaimers Apply